Dissolved oxygen measurements in brewery systems.

Krebs, W.M.

Abstract
Analytical techniques for dissolved oxygen measurements and the advantages of using the membrane covered oxygen electrode IL 530 are discussed. It is a modified Clark electrode with a wire cathode of Pt, Au or Ag and an anode of Ag coated with AgCl in a chloride containing electrolyte. The membrane isolates the electrode both electrically and chemically from the sample environment and provides a constant dominant impedance regulating O₂ transport ('flux') from sample to cathode. The flux depends on the thickness and permeability of the polymeric membrane material, silicone rubber being the most and polypropylene, Mylar and Saran the least permeable. The electrode is temperature controlled, has excellent linearity, background and response characteristics and shows no significant rheology effects. It can be calibrated in air if air saturation values of beer and wort at appropriate temperatures are known. Alternatively, it can be calibrated to read 100 in air so that test readings express % saturation. Hydrostatic pressures normally encountered in brewing do not affect the system, unless the medium contains bubbles of O₂ containing gas and, for in-line measurment of O₂ in wort, the electrode is best placed just before the fermenting vessel. The electrode is sturdy and is recommended as offering increased accuracy and versatility for static or in-line applications with wort and beer.
Keywords: analysis brewing equipment measurement oxygen wort